1. Field of the Invention
The invention relates to an apparatus, in particular a laser hybrid welding head, for a laser hybrid welding process, as well as a cross jet guide device for a laser hybrid welding process, of the type defined in claims 1 and 14.
2. Description of the Prior Art
Apparatus is already known, in particular laser hybrid welding heads, for a laser hybrid welding process, in which a laser and laser optics or an optical focussing unit and a welding torch are disposed on a mounting plate. A cross jet guide device co-operates with the laser and the optical focussing unit in order to form a cross jet, the cross jet guide device being connected to a compressed air supply system by an incoming line and an outgoing line. As a result of the so-called cross jet, the optical system of the laser or the laser optics or the optical focussing unit are shielded from any weld splatter generated during welding processes. The incoming line and the outgoing line are provided on either side of the laser and the laser optics or the optical focussing unit. When using apparatus of this type during a welding process, the surface of the workpiece is heated by the premature laser and laser optics or the optical focussing unit or melting may be initiated below the surface of the workpiece due to focussing on the focal point or burning to a certain depth due to the laser beam, so that during the subsequent arc welding process the burned depth becomes even greater resulting in a welding bead due to the delivery of a welding wire or an additional material.
The disadvantage of this situation is that a considerable amount of space is needed to run the incoming and outgoing line on either side, which significantly increases the size of a laser hybrid welding head of this type.
Devices for generating a cross jet are also known, in which an outlet element and an inlet element for compressed air are provided on either side of the laser and laser optics or optical focussing unit, enabling a cross jet, in other words an air flow, to be generated between the outlet element and the inlet element to pick up any loose metal debris.
The disadvantage of this system is that the cross jet produced by this structure is necessarily large in terms of surface area, resulting in a very high vacuum pressure in the region of the cross jet, making it necessary to dispose the latter at a large distance from a welding process when operating with a shielding gas atmosphere to prevent it from being sucked away.
Documents U.S. Pat. No. 5,981,901 A, U.S. Pat. No. 5,814,786 A and EP 0 618 037 A describe methods and devices for laser welding, in which a cross jet guide device is used to protect against welding splatter. The cross jet guide device is provided in the form of an elongate housing and a compressed air supply system is disposed on one side of the housing to deliver compressed air to create a cross jet in the interior, which then leaves the housing from the oppositely lying side of the housing. The housing also has an end-to-end orifice for a laser beam, which extends through the orifice.
The disadvantage of this approach is that a cross jet guide device of this design requires a large amount of space and is of large structural dimensions because the incoming and outgoing lines for the compressed air are arranged on either side of the housing. Consequently, a cross jet guide device of this type can only be used for a pure laser welding process.
Patent specification WO 00/24543 A also discloses a laser hybrid welding head, the laser of which is disposed at the centre. On either side of the laser a respective welding torch is mounted by means of a common mounting rail and can be displaced by means of the mounting rail.
This disadvantage of this structure is that it does not permit the use of a cross jet guide device and the laser optics become soiled by welding debris after a short welding time, which sharply reduces the power of the laser.